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Decomposição de folhada de quatro espécies florestais no Norte de Portugal: taxa de decomposição e evolução da composição estrutural e do teor em nutrientes
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Orientador(es)
Resumo(s)
Decomposition of senescent leaves of Castanea sativa (CS), and needles of Pinus pinaster (PP), Pinus nigra (PN) and Pseu-
dotsuga menziesii (PM) was studied during 3.1 to 3.5 years through weight loss and nu-
trient concentration evolution, using the litter bag technique, whereas the variation of chemical structural compounds was followed during 391 to 518 days. The highest contents of N were measured in PM and CS (respectively 14.5 and 12.1 g kg-1), which showed lower C/N ratio (39.0, 46.8) than PN and PP (122.2 and 147.7, respectively).
Highest contents of Ca (9.1 g kg-1) and of alcohol and water soluble compounds (384 against 95 to 160 g kg-1 to other species) were measured in PM needles, which also showed the lowest contents of holocelulose (253 g kg-1 against about 500 g kg-1 in the other species). The lignin Klason/N ratio decreased according to PP>PN>PM>CS,
(71.2, 58.3, 20.5 and 20.3 respectively), and the holocelulose/lignin ratio ranged from 0.9 (PM) to 1.9-2.1 in the other species. Annual decay rates, according to the negative exponential model, were ordered according to CS>PN>PM>PP (respectively -0.35, -0.27, -0.19 and -0.16), but with higher values during the first year for CS (-0.60) and PM (0.31). Soluble compounds and hemicelulose strongly decreased during the decomposition period, while lignin and cellulose amounts showed a low variability, mainly in PP and PM needles. Nutrient amounts decreased during the decomposition process, but remaining quantities for N (41 to 121 %) and P (33 to 104 %) were higher than those estimated for K, Ca and Mg (respectively 17 to 65%, 30 to 60 % and 18 to59%). A strong decreasing of C/N ratio was observed especially for PP and PN, where reached 53.2 and 47.1.
Descrição
Palavras-chave
castanea sativa pinus pinaster pinus nigra pseudotsuga menziesii litterfall decomposition structural components nutrient dynamics
Contexto Educativo
Citação
"Revista de Ciências Agrárias". ISSN 0871-018X. 32:1 (2009) 223-237
Editora
Sociedade de Ciências Agrárias de Portugal